rooted x w/ miui ics.. slow 3g?

I recently rooted my phone, and ran it stock/rooted for a while.. eventually overclock/undervolt for a while, and loved it so decided to try a ROM a few days ago.. everything's good, got all my apps restored.. no glitches/bugs anywhere.. BUT my internet/3G has slowed down drastically, like to the point of can't even get a youtube video to load, or any apps that require 3g services take forever to load.. browser is decent, but only on things like google, or a mobile site, anything else is out of the question.. I haven't tried a tether to see how the speeds are with it but is there any fix to this? a new ROM, updated modem (idk?), FBS to stock?